Steve Harris wrote:
> On 2011-04-18, at 23:06, Richard Cyganiak wrote:
>
>> Hi Pat,
>>
>> I'll push back. I understand the value of the RDF Semantics document in that it defines the valid entailments of an RDF graph. I still do not understand what role it has beyond that, and how it is relevant to operations that do not involve entailment.
>>
>> (Just to keep the underlying question in mind: We disagree on the question whether the RDF Semantics document needs to mention aspects of RDF that do not involve entailment. I think it doesn't have to, and shouldn't. You disagree.)
>>
>> On 17 Apr 2011, at 00:10, Pat Hayes wrote:
>>>> My understanding is that the RDF Model Theory exists to define which inferences are valid, given an RDF graph. What other purpose does it serve?
>>> It defines what RDF means.
>> No, it doesn't, and I think this is not a very honest statement. If the MT defined what the RDF language means, then it would have to define what an utterance in that language means. The meaning of RDF is in all the weird and wonderful technological, social and economic processes and conventions that establish, more or less reliably, the referents of URIs. Those processes are not described in the Model Theory (or, for the most part, in any other W3C Recommendation), to the contrary, the MT explicitly punts on most of them. The MT provides some icing on top of that magnificent mess.
>>
>>> Or to be achingly precise, it puts constraints upon what RDF can possibly mean.
>> I guess that's a fair characterization.
>>
>>> To give just two examples, it implies that the truth of an RDF triple cannot depend upon the form of a URI (other than by this form changing what the URI denotes) and it specifies that any URI must be interpreted as referring to the same entity every place it occurs.
>> The first of those I don't understand. The second I don't think is quite true, as the spec is only concerned with *single RDF graphs*, and AFAIK specifies nothing regarding the interpretation of URIs in different graphs.
>>
>>> These constraints on meaning apply to any RDF processing, not just to entailment checking. SPARQL for example satisfies semantic conditions which are related to the RDF semantics.
>> Can you give me an example of such a semantic condition satisfied by SPARQL that is not covered by entailment?
>>
>>> And I insist that this - the semantics of the triples - is not something that can be ignored while conforming to the RDF specs.
>> You say that to conform to the RDF specs, one must not ignore the semantics of the triple. What does this mean, ignoring the semantics of the triple? How can I tell wether I'm ignoring the semantics of a triple or not?
>>
>> Does the Model Theory gives rise to any test cases or conformance criteria?
>>
>> This is a honest question.
>>
>>> Of course, the specs can be ignored, and no doubt often are. But our job is to write the specs., so we are rather obliged to take them seriously.
>> Rest assured that I am taking the specs seriously. But I am also doing my best to take the users of RDF seriously. It is my belief that if they often ignore the specs, then we should be open to the possibility that something is wrong with the specs, and maybe it can be fixed.
>>
>>> Well, if that is your view, then by all means let us as a WG declare that RDF has no normative model theory, and is simply a meaningless notation.
>> XML and JSON and CSV and the relational model don't have normative model theories. Does that make them â€œmeaningless notationâ€